Dehydrohalogenation of halogenated orgeanic compounds



Patented June 22, 143

. TS PT FFEQE DEHYDROHALOGENATION F HALOGEN- ATED ORGANEC COMPOUNDSMichigan No Drawing. Application December 24, 1938, Serial No. ZQ'LGZS(Cl. MSW-654) 13 Claims.

This invention concerns an improved method of splitting hydrogen halidefrom halogenated organic compounds by means of alkali.

The dehydrohalogenation of organic compounds by means of alkali is awell known gen-- eral reaction which has been applied in splittinghydrogen halide from a wide variety of halogenated organic compounds toproduce numerous unsaturated organic compounds. The reaction has beenapplied in making: ethylene from ethyl bromide, vinyl chloride fromethylene chloride, acetylene from vinyl bromide, l-chloro propylene frompropylidene chloride, 2-bromopropylene from acetone dibromide, allylenefrom l-bromo propylene, cyclohexane from cyclohexyl chloride, acetylenedicarboxylic acid from dibromo succinic acid, beta-methylcrot/onaldehyde from the acetal of bromo-isovaleraldehyde, etc. A commoncharacteristic of the organic reactants for such reactions is that theyeach contain in a non-aromatic, i. e., an aliphatic or alicyclic,portion of the molecule the radical wherein X represents halogen.

The reaction has usually been carried out by heating the organicreactant with a solution of potassium hydroxide in a monohydric alcoholsuch as ethanol, but in certain instances sodium hydroxide has been usedin place of potassium hydroxide or water has been used instead of thealcohol. Usually these substitutions decrease the rate of reaction orthe yield of the desired unsaturated product.

We have now discovered that polyhydric alcohols and hydroxy-ethers arehighly active promoters for the dehydrohalogenation of halogenatedorganic compounds with alkali and that by carrying such reaction out inthe presence of a polyhydric alcohol or a hydroxy-ethcr, either sodiumhydroxide or potassium hydroxide may be used as the alkaline reactantand the latter may be employed in solid form or dissolved in an alcoholor water, as desired. The polyhydric alcohol or its ether apparentlyserves as a dehydrohalogenation catalyst, since it need only be presentin small proportion to be effective, but it may also have otherfunctions in the reaction. For convenience, it will hereinafter bereferred to as a catalyst.

Among the various polyhydric alcohols and hydroxy-ethers which may beused to promote dehydrohalogenation reactions in accordance with theinvention are thylene glycol, diethylene i'thers, e. g. poly-glycols,are even more effective.

Among the poly-glycois, we have observed that the catalytic activitybecomes greater as the number oi glycol residues (and therefore ethergroups) in the molecule is increased. For instance, diethylene glycol ismore active than ethylene glycol as a catalyst; triethylene glycol ismore active than diethylene glycol, tetraethylene glycol is more activethan triethylene glycol, etc.

The halogenated organic reactant may be any of those capable of beingdehydrohalogenated with alkali by the known methods hereinbeforediscussed. However, the invention is particularly concerned with thedehydrohalogenation of saturated polyhalo aliphatic hydrocarbons such asethylene chloride or bromide, propylene chloride or bromide, butylenechloride or bromide, trichloro ethane, t trachloro ethane, etc. toproduce corresponding halogenated olefines, e. g. vinyl chloride orbromide, chloro propylene, chloro butylene, dichloro ethylene, trichloroethylene. etc.

The alkaline reactant may be sodium hydroxide, potassium hydroxide orany other alkali which is effective in dehydrohalogenating halogenatedorganic compounds by the previously known methods hereinbeforementioned.

The reactants may be used in any desired proportions and the catalyst,i.-e., polyhydric alcohol or hydroxy-ether, may also be used in nearlyany proportion, but there are certain preferred proportions of thereactants, which may vary somewhat, depending upon the result desiredand there is a minimum proportion of catalyst below which the desiredactivation of the reaction is not attained. In general when it isdesired to split only one molecule of hydrogen halide from apolyhalogenated organic compound capable of losing two or more moleculesof hydrogen halide the organic reactant is used in a. proportionexceeding the molecular equivalent of the alkali. When two molecules ofhydrogen halide are to be split from the organic reactant the latter mayof course be used in a smaller proportion. The minimum operableproportion of catalyst is dependent somewhat upon the particularreactants and catalyst employed but usually 0.001 mol of catalyst permol of alkali is aseaasa lyst may of course be used in as large aproportion as desired. The mixture is heated, preferably with stirring,to the reaction temperature which usually is between 50" and 150 C. Inmost in- 5 stances the mixture is heated at atmospheric sufficient topromote the reaction. pressure and the unsaturated organic product Theprocedure followed in carrying the reaction is distilled off as it isformed, but there may be out in the presence of the catalyst maycorreinstances where it will be desirable to heat the spend $0 thoseheretofore p y when p ratmixture under pressure in a bomb or autoclaveme without catalysts, i. 6-. a mixture of the re- 10 and to distill theproduct after completing the actants and catalyst may be heated whennecesreaction. In many instances the product is resary, to a reactiontemperature in the presence covered directly in substantially pure form,but or absence of a medium such as water or a monowhen necessary it maybe further purified in hydric alcohol and the desired organic productknown manner, e. g., by distillation. may be distilled during orsubsequent to the i'e- Th following examples illustrate several waysaction. By using the more active of our catalysts. in which theprinciple of the invention has been the reaction may sometimes bestarted at room applied, but they are not to be construed aslimittemperature and carried to completion without ing the invention,adtdin g heat other than that generated by the re- Example 1 ac ion.

The advantages of using the catalyst are great e pe e Of this example isto demonstrate est, of course, when operating under conditions (1) theeflficiency of polyhydric alcohols and bywhieh would permit, atisfactoryreaction droxy-ethers as catalysts for a dehydrohalogenawithout aid ofthe catalyst. Thus, alcoholic po- U011 reacbioh; (2) that 911 t yst isfar more tassium hydroxide solutions are in themselves eieffective h amohohydllc alcohol h p m g fective dehydrohalogenating agents and whilea the Feactlon; and that me lfeactlon W111 3- reaction carried out withalcoholic potassium hy- (MI in the presence Water. but s retarded whendroxide may be promoted by the addition of a p r s 01 Water are used. Ineach of polyhydric alcohol or its ether, the advantages 3 Series Of e la t e ixture havof using the catalyst may not be great. It is mg thecomposition given in the iollowrng table when attempt is made to lessenthe cost of carwas heated under reflux with stirring lor the ryin outsuch reac on b it n h monoperiod of time also given in the table,whilepasshydric alcohol medium or by substituting sodium e y Vinylchloride evolved from the mixture hydroxide or other alkali in place ofpotassium into a trap, cooled with an acetone and carbon hydroxide thatthe advantages of employing the 3% dioxide mixture, where it wascondensed and colcatalyst become greatest. Accordingly, th inlected. Inthose experiments wherein water was vention is particularly directed tooperating with o s e a medium, the Sedulm hydroxide Was the catalyst inthe absence of the usual monoemployed in a solid flaked form which wasnearly hydric alcohol medium using sodium hydroxide anhydrous. The tablegives the quantities of maas the alkaline reactant. terials employed andthe yields of vinyl chloride,

Operation in the preferred manner just inbased both upon the sodiumhydroxide employed dicated may be carried out in the presence or abandupon the sodium hydroxide reacted. Th sence of water, but we have found,when using glycol residue mentioned in the table is a mixour catalysts,that water tends to retard the reture of diethylene glycol, triethyleneglycol, etc., action; hence we preferably operate in the subobtained inthe manufacture of ethylene glycol.

TABLE Reaction mixture Vinyl chloride it i 11'? Catalyst p e i-io diPercent Percent cnnci, NaOll 1110 hours arms yl logl) 11 grams gramsmama Kind Grams used consumed 54 N -5 l) (l i it :2 l l. U, U, 3 10c 4654 Glycol residue" :1. 5 20 27. s 96 4 lot) 40.2 19.8 None z (I) (l) 5iou 40.2 19.8 G ycol residue 2 g 32 I 51 97 U 100 4U 10 f0 0 l h (Z) 7we in lU Glycol new 2 1.5 I 44 I 10.4 98 2: 1w 4U None None" :i (J) (J)(3) s loo 40 None ChhOLi. t a; 15 24 96 lo 100 4U None (XHHOH amylalcohol z s i 4 n) (4) 11 mo to None Ethylene glycol 1 f5 is gas 259 13mo in None Ethylene glycol l 5 -il$ .8 04.1 9.3

13 on 40 None Di-ethylene glycol... 0.2 10.3 hit) i4 100 40 NoneDi-etbylene glycoL. 2 .5? .la 0.2 9:;

15 100 -10 None Beta-ethoxy ethanol... .5 un; .95

it 100 iu None Beta-pheno xy ethanol. 2 5.5 2.3 50.5 as

l? 100 -ll) None Bett1i1-(4-t1ertiary-butyl phenoxy) 2 5.5 2a 40 91) 1No observable reaction. 1 Only 2.5%oitl1e NeOli reacted.

stantial absence of water. The organic reactant is preferably mixed withthe desired proportions of solid comminuted sodium hydroxide and thepolyhydric alcohol or hydroxy-ether catalyst. About 1 mole of thecatalyst is usually employed Only 0.05% of the NiiOll reacted.

4 Only 4% of the N1105 reacted.

In the above table, comparison of run 1 with run 3, of run 4 with run 5,of run 6 with run "I, and of run 8 with runs 11-17 will show thatglycols and hydroxy-ethers are very effective catalysts for thereaction. A comparison of run 2 per 100 moles of sodium hydroxide, butthe catawith run 3 and of runs 9 and 10 with runs 11-17 will demonstratethat the glycols and hydroxyothers are far more efiective thanmonohydric alcohols in promoting the reaction. Runs 11-17 when comparedwith one another, indicate that hydroxy-et-hers are usually more activethan a simple glycol as catalysts. The table also shows that the newcatalysts are efiective in promoting the reaction, regardless oiwhetheror not water is present as a reaction medium, but that the reactionoccurs more favorably as the proportion of water is decreased. A smallproportion of water, e. t:., water in amount representing 20 per cent orits; of the weight of alkali. is usually not detrimental and may evenl'iivor thireaction. but the'pr sence of a larger proportion oi writ-rtends to retard thrreaction.

Trichloro-ethane was heated with naked sodium hydroxide to 90" C. Noreaction was observable. A mixture of 1500 grams of trichloro ethane,200 grams of flaked sodium hydroxide. and 1 gram of poly-ethylene glycola mixture of diethylene glycol. triethylene glycol, etc.) was heatedwith stirring at a temperature of 90 C.. whereupon vapors ofasymmetrical dichloro eth ylene were evolved. The vapors were cooled tocondense the product, After 8.5 hours 01 heat ing 470 grams of dichloroethylene had been collected and only 0.2 gram of sodium hydroxideremained unreacted. There was recovered 831 grams of unreactedtrichloro-ethanr. The yield of dichloro-ethylenc was 97 per cent oftheoretieal based on the sodium hydroxide initially employed and 96 percent of theoretical based on the trichloro-ethane consumed.

Example 3 A mixture of 385 gram. of llnsymniclriciil tetrachloro-ethane,60 grams of ilaked sodium hydroxide and Oil gram oi poly-ethylene glycolwas heated with stirring to a temperature of 60" 0.. whereupon avigorous reaction occurred, the temperature rose spontaneously to 110"(3., and trichloro ethylene started distilling from the mixture. Themixture was maintained at 110" C. for 1.5 hours, at the end of whichtime only 0.6 gram of the sodium hydroxide remained unreacted. The yieldof trichloro-ethylene was practically quantitative, based both upon thesodium hydroxide employed and upon the tetrachloro ethane consumed.

Example 4 To a mixture of 100 grams of ethylene chloride and 40 grams offlaked sodium hydroxide. 2 grams of tetraethylene glycol was added. Thereaction started at room temperature immediately after addition of thetetraethylene glycol. as evidenced by the fact that vinyl chloride wasevolved and the temperature rose spontaneously to about 60' C.. where itwas held by cooling the reaction vessel with water for about 0.5 hour.The reaction subsided about 1.5 hours after its start. No external heatwas applied at any stage of the reaction. During the reaction, thevapors evolved were passed into a cooler, wherein the vinyl chlorideproduct was condensed. 43 grams of vinyl chloride was collected. 10grams of sodium hydroxide remained unreacted after the reaction hadsubsided. The yield of vinyl chloride was 68.8 per cent of theoretical,based on the sodium hydroxide initially employed, or 91.8 per cent basedon the sodium hydroxide consumed.

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The invention may be practiced in still other ways. For instance, thesodituri hydroxide may, if desired, be employed in aqueous or alcoholicsolution, although, as hereinbefore pointed out, the employment of analcohol medium involves unnecessary expense and the presence of waterretards the rate of reaction. However, we have successfully used a 40per cent by weight concentrated aqueous sodium hydroxide solution indehydrohalogenation reactions carried out in the presence of ourcatalyst. Potassium hydroxide may, of course, be used in place of sodiumhydroxidc, but there usually is no advantage in iii-aking suchsubstitution. Neutral inorganic salts such as sodium chloride, sodiumsulphate. etc., do not have detrimental elfect on the reac- Lion.

in the lolloning claims, the generic term poly-glyc0l refers to thedi-hydroxy ether-s derived from two or more molecules of a simpleglycol. Examples of poly-glycols are diethylene glycol, triethyleneglycol, tetraethylcne glycol, dipropylene glycol, etc.

Other modes of applying the principle of the invention may be employedinstead of those explained, change being made as regards the methodherein disclosed, provided the step or steps stated by any of thefollowing claims or the equivalent of such stated step or steps beemployed.

We therefore particularly point out and distinctly claim as ourinvention:

1. In a method of splitting a hydrogen halide from the molecule of ahalogenated aliphatic hydrocarbon by reacting the latter with an alkali,the step of promoting the reaction by carrying it out in the presence ofa minor proportion of an aliphatic polyhydric alcohol.

2. In a method of splitting hydrogen halide from the molecule of ahalogenated aliphatic hydrocarbon by reacting the latter with an alkalimetal hydroxide, the step of promoting the reaction by carrying it outin the presence of a catalytic amount of a polyglycol.

3. In a method of making vinyl chloride by reacting ethylene chloridewith an alkali, the step of promoting the reaction by carrying it out inthe presence of a catalytic amount of a compound selected from the classconsisting of aliphatic hydroxy-ethers, aryloxy-aliphatic alcohols, andaliphatic polyhydric alcohols.

4. In a method of making asymmetric dichloro ethylene by reactingtri-chloro ethane with an alkali, the step of promoting the reaction bycarrying it out in the presence of a catalytic amount of a compoundselected from the class consisting of aliphatic hydroxy-ethers,aryloxyaliphatic alcohols, and aliphatic polyhydric alcohols.

5. In a method of making tri-chloro ethylene by heating tetra-chloroethane with an alkali, the step of promoting the reaction by carrying itout in the presence of a catalytic amount of a compound selected fromthe class consisting of aliphatic hydroxy-ethers, aryloxy-aliphaticalcohols, and aliphatic polyhydric alcohols.

6. In a method of splitting hydrogen halide from the molecule of ahalogenated aliphatic hydrocarbon by reacting the latter with sodiumhydroxide, the step of promoting the reaction by carrying it out in thepresence of a minor proportion of a compound selected from the classconsisting of aliphatic hydroxy-ethers, aryloxyaliphatic alcohols andaliphatic polyhydric alcohols,

7. In a method of splitting hydrogen halide from the molecule of ahalogenated aliphatic hydrocarbon by reacting the latter with sodiumhydroxide, the step of promoting the reaction by carrying it out in thepresence of a catalytic amount of a polyglycol.

8. In a method of splitting hydrogen chloride from the molecule of achlorinated aliphatic hydrocarbon by reacting the latter with sodiumhydroxide, the step of promoting the reaction by carrying it out in thepresence of a catalytic amount of a polyglycol.

9. In a method of making vinyl chloride by reacting ethylene chloridewith sodium hydroxide, the step of promoting the reaction by carrying itout in the presence of a minor proportion of a polyglycol.

10. In a method of making a symmetric dichloro-ethylene by reactingtrichloro-ethane with sodium hydroxide, the step of promoting thereaction by carrying it out in the presence of a catalytic amount of apolyglycol.

11. In a method of making trichloro-ethylene by reactingtetrachloro-ethane with sodium hydroxide, the step of promoting thereaction by carrying it out in the presence of a catalytic amount ofpolyglycol.

12. In a method wherein an alkali is reacted with an organic compoundcontaining a hydrogen atom and a halogen atom attached to adjacentcarbon atoms in a non-aromatic part of the molecule to split hydrogenhalide from the molecule and form an unsaturated linkage between saidadjacent carbon atoms, the step of promoting the reaction by carrying itout in the presence of a minor proportion of a compound selected fromthe class consisting of aliphatic hydroxy-ethers, aryloxy-aliphaticalcohols and aliphatic polyhydric alcohols.

13. In a method wherein an alkali is reacted with an organic compoundcontaining a hydrogen atom and a chlorine atom attached to adjacentcarbon atoms in a non-aromatic part of the molecule to split hydrogenchloride from the molecule and form an unsaturated linkage between saidadjacent carbon atoms, the step of promoting the reaction by carrying itout in the presence of a minor proportion of a compound selected fromthe class consisting of aliphatic hydroxy-ethers, aryloxy-aliphaticalcohols and aliphatic polyhydric alcohols.

CHARLES J. STROSACKER. FORREST C. AMSTUTZ.

